Casting method for making a lightweight concrete product

ABSTRACT

A structural lightweight concrete composition comprising cement, a fine aggregate such as sand, a natural coarse aggregates, such as limestone, scoria or perlite or mixtures thereof, a synthetic coarse aggregate comprising a polymeric material, such as polypropylene beads, an industrial waste byproduct in the form of fine particles, such as silica fume or heavy oil ash, a superplasticizer, such as a polycarboxylate ether and water demonstrating lower thermal conductivity and sufficient compressive strength. Concrete products made therefrom and methods for producing such products are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of Ser. No. 15/084,653, nowallowed, having a filing date of Mar. 30, 2016.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure relates to structural lightweight concretecompositions that offer low thermal conductivity, more particularlycement/aggregate compositions comprising a natural coarse aggregate, apolymeric synthetic coarse aggregate and industrial waste byproduct fineparticles, concrete products made therefrom and methods for producingsuch products.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Lightweight concrete (LWC) is a conglomerate of cement and lightweightaggregates. It has a bulk density ranging between 300 and 2000 kg/m³compared to a value of 2200 to 2600 kg/m³ for normal weight concrete(NWC). Some of the advantages of using lightweight concrete include, i)reduction in the dead load, ii) lighter and smaller elements, iii) highthermal insulation, and iv) enhancement in fire resistance. According tothe American Concrete Institute (ACI) standards [ACI 213—incorporatedherein by reference in its entirety], structural lightweight concrete(SLWC) is a concrete that is prepared with lightweight aggregates andwhose average unit weight ranges from 1400 to 1900 kg/m³ anddemonstrates a compressive strength greater than 17.0 MPa. Structurallightweight concrete provides technical, environmental, and economicaladvantages and has quickly become a material of the future as the worldgrows more conscious of energy conservation.

There are clear advantages of structural lightweight concrete overnormal weight concrete. For example, structural lightweight concrete hasa greater strength/weight ratio, lower thermal conductivity, superiorfire resistance, and enhanced durability properties. In addition, theuse of structural lightweight concrete decreases the dead load, whichleads to a reduction in the size of columns, beams, walls andfoundations that reduces resulting seismic loads and earthquake damage,which are proportional to the weight of the structure. However, the mostsignificant potential advantage to the use of structural lightweightconcrete is environmental protection. If the raw materials needed forthe production of structural lightweight concrete can be derived fromnatural sources and industrial waste products, the environment andeconomy stands to benefit. In addition, the use of structurallightweight concrete can result in a significant reduction in greenhousegas emissions by reducing the need for larger quantities of cement whoseproduction is a major contributor to CO₂ emissions.

In view of the forgoing, one object of the present disclosure is toprovide structural lightweight concrete compositions with high thermalinsulation that utilize natural aggregates, polymeric syntheticaggregates and industrial waste byproducts in the disclosed materials. Afurther aim of the present disclosure is to provide structurallightweight concrete products comprising said compositions and toprovide methods for producing said structural lightweight concreteproducts.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure relates to astructural lightweight concrete composition comprising i) cement, ii) afine aggregate, iii) a natural coarse aggregate, iv) a synthetic coarseaggregate comprising a polymeric material, v) an industrial wastebyproduct in the form of fine particles, vi) a superplasticizer, andvii) water, wherein the average particle size of the fine aggregate andthe industrial waste byproduct is less than or equal to 1 mm and theaverage particle size of the synthetic coarse aggregate and the naturalcoarse aggregate is greater than 1 mm, and wherein the weight ratio ofwater to cement is in the range of 0.33 to 0.8 and is sufficient toaffect hydraulic setting of the cement.

In one embodiment, the synthetic coarse aggregate comprising a polymericmaterial is spherical polypropylene beads with an average particle sizeof 2-15 mm.

In one embodiment, the structural lightweight concrete composition has aweight percentage of the synthetic coarse aggregate comprising apolymeric material ranging from 2-15% relative to the total weight ofthe composition.

In one embodiment, the cement is present in the structural lightweightconcrete composition at 300-500 kg/m³.

In one embodiment, the structural lightweight concrete composition has aweight percentage of cement ranging from 20-30% relative to the totalweight of the composition.

In one embodiment, the fine aggregate is sand with an average particlesize of less than 700 μm.

In one embodiment, the structural lightweight concrete composition has aweight percentage of the fine aggregate ranging from 15-30% relative tothe total weight of the composition.

In one embodiment, the natural coarse aggregate is at least one selectedfrom the group consisting of limestone, perlite, and scoria.

In one embodiment, the structural lightweight concrete composition has aweight percentage of the natural coarse aggregate ranging from 20-45%relative to the total weight of the composition.

In one embodiment, the natural coarse aggregate comprises crushedlimestone having an average particle size in the range of 1-20 mm.

In one embodiment, the industrial waste byproduct is at least oneselected from the group consisting of silica fume and heavy oil ash.

In one embodiment, the structural lightweight concrete composition has aweight percentage of the industrial waste byproduct in the form of fineparticles ranging from 0.5-10%0/relative to the total weight of thecomposition.

In one embodiment, the superplasticizer is a polycarboxylate ether.

In one embodiment, the structural lightweight concrete composition has aweight percentage of the superplasticizer ranging from 0.1-2.0% relativeto the total weight of the composition.

In one embodiment, the structural lightweight concrete composition has aweight percentage of water ranging from 10-20% relative to the totalweight of the composition.

In one embodiment, the structural lightweight concrete composition has a28-day unit weight in the range of 1600-1900 kg/m³ after setting.

In one embodiment, the structural lightweight concrete composition has acompressive strength in the range of 20-40 MPa after setting.

In one embodiment, the structural lightweight concrete composition has athermal conductivity in the range of 0.3-0.7 W/(m·K) after setting.

According to a second aspect, the present disclosure relates to a methodfor producing a cast concrete product comprising the structurallightweight concrete composition in any of its embodiments, the methodcomprising i) mixing the cement, the fine aggregate, the natural coarseaggregate, the synthetic coarse aggregate and the industrial wastebyproduct in the form of fine particles to form a solid cement mixture,ii) adding water and a superplasticizer to the cement mixture to affecthydraulic setting while maintaining a slump in the range of 50-100 mm toform a fluid concrete mixture and iii) casting the concrete mixture in apredetermined shape by placing the fluid concrete mixture in a mold toproduce a cast concrete product after setting.

According to a third aspect, the present disclosure relates to a castconcrete product comprising the structural lightweight concretecomposition in any of its embodiments.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription.

DETAILED DESCRIPTION OF THE EMBODIMENTS

According to a first aspect, the present disclosure relates to astructural lightweight concrete composition comprising i) cement, ii) afine aggregate, iii) a natural coarse aggregate, iv) a synthetic coarseaggregate comprising a polymeric material, v) an industrial wastebyproduct in the form of fine particles, vi) a superplasticizer, andvii) water.

The main ingredients of concrete include, but are not limited to,cement, water, aggregates, chemical admixtures and mineral admixtures.There are many types of concretes created by varying the proportions ofthe main ingredients. In this manner or by substitution of thecementitious and aggregate phases, the finished product can be tailoredto its application with varying strength, density, or chemical andthermal resistance properties. As used herein “concrete” refers to acomposite material composed of aggregate bonded together with a fluidcement which hardens over time. In hydraulic cement concretes, when theaggregate is mixed together with the dry cement and water, they form afluid mass that is easily molded into shape. The cement reactschemically with the water and other ingredients to form a hard matrixwhich binds all of the materials together into a durable stone-likematerial that has many uses. Often, additives are included in themixture to improve the physical properties of the wet mix or thefinished material. In terms of the present disclosure, the compositionmay refer to the fresh state solid cement or concrete mixture comprisingthe cement, the fine aggregate, the natural coarse aggregate, thesynthetic coarse aggregate and the industrial waste byproduct in theform of fine particles before the addition of the water and/orsuperplasticizer, the composition may refer to a formable orself-placing fluid concrete mixture after the addition of all or aportion of the water and/or superplasticizer, and the composition mayrefer to the hardened matrix concrete after any period of setting oncethe hydration process has started. In a preferred embodiment, allcomponents of the structural lightweight concrete composition of thepresent disclosure are homogeneously dispersed in the composition.

As used herein, “structural lightweight concrete” as defined in ASTM C330 is concrete having a minimum 28-day compressive strength of 17 MPa(2500 psi) and an equilibrium density in the range of 1120-1920 kg/m³(70-120 lb/ft³). This stands in contrast to normal weight concrete. Asused herein, “normal weight concrete” refers to concrete having anequilibrium density of 2240-2480 kg/m³ (140-155 lb/ft³). This definitionis not a specification, project specifications vary by necessity. Whilestructural lightweight concrete with an equilibrium density of 1120-1680kg/m³ (70-105 lb/ft³) is infrequently used, most structural lightweightconcrete has an equilibrium density of 1680-1920 kg/m³ (105-120 lb/ft³).As used herein, “equilibrium density” as defined in ASTM 567 is thedensity reached by structural lightweight concrete after exposure torelative humidity of 50±5% and a temperature of 23±2° C. for a period oftime sufficient to reach a density that changes less than 0.5% in aperiod of 28 days.

As used herein, “structural lightweight concrete” also includesaggregate that is either entirely lightweight aggregate or a combinationof lightweight and normal density aggregate. As used herein,“lightweight aggregate” as defined in ASTM C 330 has a bulk density ofless than 1120 kg/m³ (70 lb/ft³) for fine aggregate and less than 880kg/m³ (55 lb/ft³) for coarse aggregate. As used herein, the terms “fine”and “coarse” refer to the average particle size, here the averageparticle size of the aggregate and additives of the structurallightweight concrete composition. As used herein, average particle sizerefers to the longest linear dimension of the particle. In terms of thepresent disclosure, “fine” refers to having an average particle size ofless than or equal to 1 mm, preferably less than 900 μm, preferably lessthan 800 μm, preferably less than 750 μm, preferably less than 700 μm,preferably less than 650 μm, preferably less than 600 μm, preferablyless than 550 μm, preferably less than 500 μm, preferably less than 400μm, preferably less than 300 μm, preferably less than 200 μm, preferablyless than 150 μm, preferably less than 100 μm. In terms of the presentdisclosure, “coarse” refers to having an average particle size ofgreater than 1 mm, preferably greater than 5 mm, preferably greater than10 mm, preferably greater than 15 mm, preferably greater than 20 mm,preferably greater than 25 mm, preferably greater than 30 mm, preferablygreater than 40 mm, preferably greater than 50 mm, such as for example1-20 mm, preferably 2-18 mm, preferably 3-15 mm, preferably 4-12 mm,preferably 5-10 mm. In a preferred embodiment, the average particle sizeof the fine aggregate and the industrial waste byproduct is less than orequal to 1 mm and the average particle size of the synthetic coarseaggregate and the natural coarse aggregate is greater than 1 mm. As usedherein, a “natural” aggregate refers to a natural substance derived froma mineral source. As used herein, a “synthetic” aggregate refers tosubstance or compound that is made artificially through chemicalreactions.

The structural lightweight concrete composition of the presentdisclosure comprises cement. As used herein, “cement” is a binder, asubstance that sets and hardens and can bind other materials together.Cements used in construction can be characterized as being eitherhydraulic or non-hydraulic, depending upon the ability of the cement toset in the presence of water. Non-hydraulic cement will not set in wetconditions or underwater; rather, it sets as it dries and reacts withcarbon dioxide in the air and can be attacked by some aggressivechemicals after setting. In terms of the present disclosure, the cementof the structural lightweight concrete composition may be anon-hydraulic cement, a hydraulic cement, or mixtures thereof,preferably a hydraulic cement.

Non-hydraulic cement, such as slaked lime (calcium hydroxide mixed withwater), hardens by carbonation in the presence of carbon dioxide whichis naturally present in the air. First calcium oxide is produced fromcalcium carbonate by lime calcination at temperatures above 800° C. fora period of time greater than 8 hours at atmospheric pressure. Thecalcium oxide is then slaked by mixing it with water to make slaked lime(calcium hydroxide). Once the excess water is completely evaporated(process technically called setting), the carbonation starts. Thisreaction may take a significant amount of time due to the partialpressure of carbon dioxide in the air being low. The carbonationreaction requires that the dry cement be exposed to air, for this reasonthe slaked lime is a non-hydraulic cement that cannot be used underwater. This whole process can optionally be referred to as the limecycle.

Conversely, hydraulic cement hardens by hydration when water is added.Hydraulic cements set and become adhesive due to a chemical reactionbetween the dry ingredients and water. The chemical reaction results inmineral hydrates that are not very water soluble and thus are quitedurable in water and safe from chemical attack. This allows setting inwet conditions or underwater and further protects the hardened materialfrom chemical attack. Hydraulic cements are made of a mixture ofsilicates and oxides, the four main components being: i) belite(2CaO.SiO₂), ii) alite (3CaO.SiO₂), iii) tricalcium aluminate(3CaO.Al₂O₃, also referred to as celite), and iv) tetracalcium aluminoferrite (4CaO.Al₂O₃.Fe₂O₃ or brownmillerite). In general, the silicatesare responsible for the mechanical properties of the cement, while thetricalcium aluminate and tetracalcium alumino ferrite allow theformation of the liquid phase during any sintering or firing and theycontrol the durability and performance of the cement. Combining waterwith a hydraulic cementitious material forms a cement paste by theprocess of hydration. The cement paste glues the aggregate together,fills voids within it, and makes it flow more freely. Hydration involvesmany different reactions, often occurring at the same time. As thereactions proceed, the products of the cement hydration processgradually bond together the individual aggregate particles and othercomponents of the concrete to form a solid mass. A cement notation for ageneral hydration reaction is represented by formula (I), the standardnotation for a general hydration reaction is represented by formula(II), and a balanced general hydration reaction is represented byformula (III).C₃S+H→C.S.H+CH  (I):Ca₃SiO₅+H₂O→(CaO).(SiO₂).(H₂O)(gel)+Ca(OH)₂  (II):2Ca₃SiO₅+7H₂O→3(CaO).2(SiO₂).4(H₂O)(gel)+3Ca(OH)₂  (III):

In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises cement and the cementcomprises 40-80 wt % of tricalcium silicate ((CaO)₃.SiO₂, C₃S in cementnotation) relative to the total weight of the cement, preferably 45-75wt %, preferably 50-70 wt %, preferably 52-65 wt %, preferably 54-60 wt%, preferably 56-58 wt % (CaO)₃.SiO₂ relative to the total weight of thecement. In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises cement and the cementcomprises 5-40 wt % of dicalcium silicate ((CaO)₂.SiO₂, C₂S in cementnotation) relative to the total weight of the cement, preferably 6-35 wt%, preferably 7-32 wt %, preferably 10-30 wt %, preferably 12-25 wt %,preferably 14-20 wt %, preferably 15-18 wt % (CaO)₂.SiO₂ relative to thetotal weight of the cement. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure comprisescement and the cement comprises 0.1-20 wt % of tricalcium aluminate((CaO)₃.Al₂O₃, C₃A in cement notation) relative to the total weight ofthe cement, preferably 1-15 wt %, preferably 2-13 wt %, preferably 4-12wt %, preferably 6-10 wt %, preferably 7-9 wt % (CaO)₃.Al₂O₃ relative tothe total weight of the cement. In a preferred embodiment, thestructural lightweight concrete composition of the present disclosurecomprises cement and the cement comprises 0.1-22 wt % of tetracalciumaluminoferrite ((CaO)₄.Al₂O₃.Fe₂O₃, C₄AF in cement notation) relative tothe total weight of the cement, preferably 1-20 wt %, preferably 5-18 wt%, preferably 6-16 wt %, preferably 8-14 wt %, preferably 10-12 wt %,preferably 11.25-11.75 wt % (CaO)₄.Al₂O₃.Fe₂O₃ relative to the totalweight of the cement.

In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises cement and the cementcomprises 15-25 wt % of silicon dioxide (SiO₂ or S in cement notation)relative to the total weight of the cement, preferably 19-23 wt %,preferably 20-22 wt %, or about 20.5 wt % of SiO₂ relative to the totalweight of the cement. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure comprisescement and the cement comprises 55-70 wt % of calcium oxide (CaO or C incement notation) relative to the total weight of the cement, preferably60-70 wt %, preferably 61-67 wt %, preferably 62-66 wt %, preferably63-65 wt %, preferably 64.25-64.75 wt % of CaO relative to the totalweight of the cement. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure comprisescement and the cement further comprises ferric oxide (Fe₂O₃ or F incement notation), aluminum oxide (Al₂O₃, A in cement notation), gypsum(CaSO₄.2H₂O), and anhydrite (CaSO₄). These compounds are generallypresent in less than 10 wt % relative to the total weight of the cement,preferably less than 8 wt %, preferably less than 6 wt %, such as forexample 0.1-6 wt %, preferably 2.5-6.0 wt %, preferably 3.5-5.75 wt %relative to the total weight of the cement. Other inorganic compoundsmay be present in the cement including, but not limited to, magnesium,sodium, potassium and oxides or mixtures thereof. These compounds aregenerally present in less than 2 wt % relative to the total weight ofthe cement, preferably less than 1 wt %, preferably less than 0.5 wt %,preferably less than 0.4 wt %, preferably less than 0.2 wt % relative tothe total weight of the cement.

In a preferred embodiment, the cement of the lightweight concretecomposition of the present disclosure is a hydraulic cement, preferablya sulfoaluminous clinker, preferably Portland cement. As used herein,“Portland cement” refers to the most common type of cement in generaluse around the world developed from types of hydraulic lime and usuallyoriginating from limestone. It is a fine powder produced by heatingmaterials in a kiln to form what is called clinker, grinding theclinker, and adding small amounts of other materials. The Portlandcement is made by heating limestone (calcium carbonate) with othermaterials (such as clay) to >1400° C. in a kiln, in a process known ascalcination, whereby a molecule of carbon dioxide is liberated from thecalcium carbonate to form calcium oxide, or quicklime, which is thenblended with the other materials that have been included in the mix tofrom calcium silicates and other cementitious compounds. The resultinghard substance, called “clinker” is then ground with a small amount ofgypsum into a powder to make ordinary Portland cement (OPC). Severaltypes of Portland cement are available with the most common being calledordinary Portland cement (OPC) which is grey in color. The low cost andwidespread availability of the limestone, shales, and other naturallyoccurring materials used in Portland cement make it one of the low costmaterials widely used throughout the world. However, Portland cement iscaustic, can contain some hazardous components and carries environmentalconcerns such as the high energy consumption required to mine,manufacture, and transport the cement and the related air pollutionincluding the release of greenhouse gases, dioxins, NO_(X), SO₂, andparticulates.

Clinkers make up approximately 90% of Portland cement along with alimited amount of calcium sulfate (which controls the set time) and upto approximately 5% minor constituents (i.e. filler) as allowed byvarious standards. In a preferred embodiment, clinkers are nodules withan average particle diameter of approximately 2-30 mm, preferably 5-25mm, preferably 8-20 mm of a sintered material that is produced when araw mixture of predetermined composition is heated to high temperature.The key chemical reaction which defines Portland cement from otherhydraulic limes occurs at these temperatures (>1200° C.) and is whenbelite (Ca₂SiO₄) combines with calcium oxide (CaO) to form alite(Ca₃SiO₅).

Portland cement clinkers are generally made by heating (i.e. in a cementkiln) a mixture of raw materials to a calcining temperature of above500° C. and then a fusion temperature, which is approximately 1400° C.for modern Portland cements to sinter the materials into clinker. Thematerials in Portland cement clinker are alite, belite, tricalciumaluminate, and tetracalcium alumino ferrite. The aluminum, iron, andmagnesium oxides are present as a flux allowing the calcium silicates toform at a lower temperature and do not generally contribute to strength.For specific Portland cements (i.e. low heat or sulfate resistant types)it may be necessary to limit the amount of tircalcium aluminate (3CaO.Al₂O₃) that is formed. The major raw material for the clinker makingprocess is usually limestone (CaCO₃) mixed with a second materialcontaining clay as source of alumino silicate. Often, an impurelimestone which contains clay or SiO₂ is used. The CaCO₃ content ofthese limestones can be as low as 80%. Secondary raw materials(materials in the raw mix other than limestone) depend on the purity ofthe limestone. Secondary raw materials may include, but are not limitedto, clay, shale, sand, iron ore, bauxite, fly ash, slag and the like,when a cement kiln is fired by coal, the ash of the coal may act as asecondary raw material.

Often to achieve the desired setting qualities in the finished Portlandcement product, a quantity (˜1-10 wt %, preferably 2-8 wt %, or about 5wt %) of calcium sulfate (often in the form of gypsum or anhydrite) isadded to the clinker and the mixture is finely ground to form thefinished cement powder, such as for example in a cement mill. Thegrinding process may be controlled to obtain a powder having a broadparticle size range, in which typically 15% by mass consists ofparticles below 5 μm in diameter, and 5% by mass consists of particlesabove 45 μm in diameter. The measure of fineness most closely associatedwith cement is the specific surface area, which refers to the totalparticle surface area of a unit mass of the cement. The rate of initialreaction (˜up to 24 hours) of the cement on addition of water isdirectly proportional to the specific surface area. In a preferredembodiment, the structural lightweight concrete composition of thepresent disclosure comprises cement having a specific surface areavalues in the range of 250-450 m²·kg⁻¹, preferably 275-425 m²·kg⁻¹,preferably 300-400 m²·kg⁻¹, preferably 320-380 m²·kg⁻¹. Typically,general purpose Portland cement falls within these ranges, although itmay be as high as 450-700 m²·kg⁻¹ for “rapid hardening” cements.

As used herein, “Portland cement” or “Portland cement clinker” has atricalcium silicate ((CaO)₃.SiO₂, C₃S) content of 45-75 wt % relative tothe total weight of the cement, a dicalcium silicate ((CaO)₃.SiO₂, C₂S)content of 7-32 wt % relative to the total weight of the cement, atricalcium aluminate ((CaO)₃.Al₂O₃, C₃A) content of 0-13 wt % relativeto the total weight of the cement, a tetracalcium aluminoferrite((CaO)₄.A₂O₃.Fe₂O₃, C₄AF) content of 0-18 wt % relative to the totalweight of the cement, and a gypsum (CaSO₄.2H₂O) content of 0-10 wt %relative to the total weight of the cement. Furthermore, as used herein“Portland cement or “Portland cement clinker” has a calcium oxide (CaO,C) content of 61-67 wt % relative to the total weight of the cement, asilicon dioxide (SiO₂, S) content of 19-23 wt % relative to the totalweight of the cement, an aluminum oxide (Al₂O₃, A) content of 2.5-6 wt %relative to the total weight of the cement, a ferric oxide (Fe₂O₃, F)content of 0-6 wt % relative to the total weight of the cement, and asulfate (S) content of 1.5-4.5 wt % relative to the total weight of thecement.

In general, different standards are used for classification of Portlandcement. The two major standards are the ASTM C150 used primarily in theUSA and the European EN 197. ASTM C150 defines Portland cement ashydraulic cement (cement that not only hardens by reacting with waterbut also forms a water resistant product) produced by pulverizingclinkers which consist essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulphate as aninter ground addition. The European standard EN 197-1 defines Portlandcement as ground Portland cement clinker that is a hydraulic materialconsisting of at least two thirds by mass of calcium silicates(3CaO.SiO₂ and 2CaO.SiO₂), the remainder consisting of aluminum and ironcontaining clinker phases and other compounds. The ratio of CaO to SiO₂shall not be less than 2.0 and the magnesium oxide (MgO) content shallnot exceed 5.0% by mass. The EN 197 cement types CEM I, II, III, IV andV do not correspond to the similarly named cement types in ASTM C150.

Five types of Portland cements exist, with variations in the first threeaccording to ASTM C150. Type I Portland cement is known as common orgeneral purpose cement and it is generally assumed unless another typeis specified. It is commonly used for general construction especiallywhen making precast and precast-prestressed concrete that is notintended to be in contact with soils or ground water. The typicalcompound compositions of this Type I by weight relative to the totalweight of the cement are: 55% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF),2.8% (MgO), 2.9% (SO₃), 1.0% ignition loss, and 1.0% free CaO. Alimitation on the composition is that the (C₃A) shall not exceed 15%.Type II Portland cement gives off less heat during hydration. This typeof cement costs about the same as Type I. This type is for generalconstruction exposed to moderate sulfate attack and is intended for usewhen concrete is in contact with soils and ground water. The typicalcompound compositions of this Type II by weight relative to the totalweight of the cement are: 51% (C₃S), 24% (C₂S), 6% (C₃A), 11% (C₄AF),2.9% (MgO), 2.5% (SO₃), 0.8% ignition loss, and 1.0% free CaO. Alimitation on the composition is that the (C₃A) shall not exceed 8%,which reduces its vulnerability to sulfates. Type III Portland cementhas a relatively high early strength. The typical compound compositionsof this Type III by weight relative to the total weight of the cementare: 57% (C₃S), 19% (C₂S), 10% (C₃A), 7% (C₄AF), 3.0% (MgO), 3.1% (SO₃),0.9% ignition loss, and 1.3% free CaO. This cement is similar to Type Ibut ground finer. In some cases a separate clinker with higher C₃Sand/or C₃A content may be used, ground to a specific surface area thatis typically 50-80% higher. The gypsum level may also be slightlyincreased. This gives the concrete using this Type III of cement a threeday compressive strength equal to the seven day compressive strength ofTypes I and II. The Type III seven day compressive strength is almostequal to the 28-day compressive strengths of Types I and II, thedownside being that the six month strength of Type III is the same orslightly less than that of Types I and II. Type IV Portland cement isgenerally known for its low heat of hydration. The typical compoundcompositions of this Type IV by weight relative to the total weight ofthe cement are: 28% (C₃S), 49% (C₂S), 4% (C₃A), 12% (C₄AF), 1.8% (MgO),1.9% (SO₃), 0.9% ignition loss, and 0.8% free CaO. The percentages of(C₂S) and (C₄AF) are relatively high and (C₃S) and (C₃A) are relativelylow. A limitation on this type of composition is that the maximumpercentage of (C₃A) is 7% and the maximum percentage of (C₃S) is 35%.This causes the heat given off by the hydration reaction to develop at aslower rate. However, as a consequence the strength of concrete usingthis type develops slowly, after one to two years the strength is higherthan other types after full curing. Type V Portland cement is used wheresulfate resistance is important. The typical compound compositions ofthis Type V by weight relative to the total weight of the cement are:38% (C₃S), 43% (C₂S), 4% (C₃A), 9% (C₄AF), 1.9% (MgO), 1.8% (SO₃), 0.9%ignition loss, and 0.8% free CaO. This cement has a very low (C₃A)composition which accounts for its high sulfate resistance. The maximumcontent of (C₃A) allowed is 5% for Type V Portland cement. Anotherlimitation is that the (C₄AF)+2(C₃A) composition cannot exceed 20%/a.This Type V is used in concrete to be exposed to alkali soil and groundwater sulfates which react with (C₃A) causing disruptive expansion.Types IA, IIA, and IIIA have the same composition as Types I, II, andIII with an air-entraining agent ground into the mix. Types II(MH) andII(MH)A have a similar composition to Types II and IIA, but with a mildheat. In terms of the present disclosure, the cement of the concretecomposition may be Portland cement, and may be an ASTM C150 Type IPortland cement, an ASTM C150 Type II Portland cement, an ASTM C150 TypeII Portland cement, an ASTM C150 Type IV Portland cement, an ASTM C150Type V Portland cement, a Type IA Portland cement, a Type IIA Portlandcement, a Type IIIA Portland cement, a Type II(MH) Portland cement, atype II(MH)A Portland cement or mixtures thereof, preferably an ASTMC150 Type I Portland cement.

EN 197-1 defines five classes of common cement that comprise Portlandcement as a main constituent. These classes differ from the ASTMclasses. CEM Class I Portland cement comprises Portland cement and up to5 wt % relative to the total weight of the cement of minor additionalconstituents. CEM Class II Portland-composite cement comprises Portlandcement and up to 35 wt % relative to the total weight of the cement ofother single constituents. CEM Class III blast furnace cement comprisesPortland cement and higher percentages of blast furnace slag. CEM ClassIV pozzolanic cement comprises Portland cement and up to 55% ofpozzolanic constituents (i.e. volcanic ash). CEM Class V compositecement comprises Portland cement, blast furnace slag or fly ash andpozzolana. Constituents that are permitted in Portland-composite cementsare artificial pozzolans (i.e. blast furnace slag, silica fume, and flyashes) or natural pozzolans (i.e. siliceous or siliceous aluminousmaterials such as volcanic ash glasses, calcined clays and shale). Interms of the present disclosure, the cement of the concrete compositionmay be Portland cement, and may be a CEM Class I cement, a CEM Class IIcement, a CEM Class III cement, a CEM Class IV cement, a CEM Class Vcement or mixtures thereof.

It is equally envisaged, that the present disclosure may be adapted toincorporate white Portland cement. White Portland cement or whiteordinary Portland cement (WOPC) is similar to ordinary grey Portlandcement in all respects except for its high degree of whiteness. The mainrequirement is to have low iron content which should be less than 0.5 wt% relative to the total weight of the cement expressed as Fe₂O₃ forwhite cement and less than 0.9 wt % for off-white cement. In certainembodiments, the iron oxide as ferrous oxide (FeO) obtained via slightreducing conditions (zero excess oxygen in the kiln) may give theclinker and cement a green tinge. Other metals including, but notlimited to, Cr, Mn, Ti, etc. can also in trace content give color tingesto the cement of the present disclosure.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise othercements. Exemplary suitable cements that may be used in addition to, orin lieu of a Portland cement or an ASTM C150 Type I Portland cementinclude, but are not limited to, Portland cement blends such as Portlandblast furnace slag cement (or blast furnace cement), Portland fly ashcement, Portland pozzolan cement, Portland silica fume cement, masonrycements, expansive cements, white blended cements, colored cements, veryfinely ground cements, pozzolan lime cements, slag lime cements,supersulfated cements, calcium sulfoaluminate cements, “natural” cementsand geopolymer cements, and the like and mixtures thereof.

As used herein, specific gravity is the ratio of the density of asubstance to the density of a reference substance; equivalently, it isthe ratio of the mass of a substance to the mass of a referencesubstance for the same given volume. Apparent specific gravity is theratio of the weight of a volume of the substance to the weight of anequal volume of the reference substance. As used herein, the referencesubstance is water at a temperature 2-25° C., preferably 4-22° C. and apressure of approximately 1 atm (˜101 kPa). In a preferred embodiment,the structural lightweight concrete composition of the presentdisclosure comprises cement having a specific gravity of 2.0-4.0,preferably 2.5-3.5, preferably 2.75-3.4, preferably 3.0-3.3, preferably3.1-3.2, or about 3.15. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure has a weightpercentage of the cement ranging from 20-30% relative to the totalweight of the composition, preferably 22-28%, preferably 23-26%,preferably 23-25%, or about 24% relative to the total weight of thestructural lightweight concrete composition. In a preferred embodiment,the structural lightweight concrete composition of the presentdisclosure has cement present in the composition at 300-500 kg/m³relative to the total volume of the composition, preferably 320-480kg/m³, preferably 340-460 kg/m³, preferably 360-440 kg/m³, preferably380-420 kg/m³, or about 400 kg/m³ relative to the total volume of thecomposition.

The structural lightweight concrete composition of the presentdisclosure also comprises water. Cement sets when mixed with water byway of a complex series of chemical reactions. The differentconstituents slowly crystallize and the interlocking of their crystalsgives cement its strength. Carbon dioxide is slowly absorbed to convertthe Portlandite (Ca(OH)₂) into soluble calcium carbonate. When water ismixed with cement, the product sets in a few hours and hardens over aperiod of weeks. These processes can vary widely depending on the mixused and the conditions of curing the product. After the initialsetting, immersion in warm water will speed up setting; in someembodiments gypsum may be added as an inhibitor to prevent flashsetting. In principle, the strength continues to rise slowly as long aswater is available for continued hydration, but concrete is usuallyallowed to dry out after a few weeks causing strength growth to stop. Ina preferred embodiment, the structural lightweight concrete compositionof the present disclosure has a weight percentage of the water rangingfrom 10-20% relative to the total weight of the composition, preferably12-20%, preferably 14-20%, preferably 15-19%, preferably 16-18% relativeto the total weight of the structural lightweight concrete composition.

In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure has a weight ratio of water tocement in the range of 0.33-0.8, preferably 0.33-0.75, preferably0.33-0.70, preferably 0.33-0.65, preferably 0.33-0.6, preferably0.33-0.55, preferably 0.35-0.50, preferably 0.375-0.45, or about 0.4 andis sufficient to affect hydraulic setting of the cement. A lower waterto cement ratio yields a stronger, more durable concrete, whereas morewater gives a freer flowing concrete with a higher slump. Impure watercan be used to make the concrete herein, but can cause problems whensetting or in causing premature failure of the structure. In a preferredembodiment, the water of the structural lightweight concrete compositionof the present disclosure is potable water.

The structural lightweight concrete composition of the presentdisclosure also comprises aggregates. As used herein, “constructionaggregate” or simply “aggregate” refers to a broad category ofparticulate material used in construction. Exemplary materials include,but are not limited to, sand, gravel, crushed stone, slag, recycledconcrete, geosynthetic aggregates and the like. Aggregates are acomponent of composite materials, such as concrete; the aggregates serveas reinforcement to add strength to the overall composite material. TheASTM publishes a listing of specifications including, but not limitedto, ASTM D 692 and ASTM D 1073 for various construction aggregateproducts, which by their individual design are suitable for specificconstruction purposes. The products include specific types of coarse andfine aggregate designed for such uses as additives to concrete mixes.Fine and coarse aggregates make up the bulk of a concrete mixture. Sand,natural gravel, and crushed stone are used mainly for this purpose.Recycled aggregates (from construction, demolition, and excavationwaste) are increasingly used as partial replacements for naturalaggregates, while a number of manufactured aggregates, includingair-cooled blast furnace slag and bottom ash also find use. The presenceof aggregate greatly increases the durability of concrete above that ofcement, which is a brittle material in its pure state, and also reducescost and controls cracking caused by temperature changes. Thus concreteis a true composite material. Sources of these basic materials can begrouped into three main areas: mining of mineral aggregate deposits(i.e. sand, gravel and stone), the use of waste slag from themanufacture of iron, steel and petroleum products or recycling ofconcrete (itself chiefly manufactured from mineral aggregates), andobtaining some materials that are used as specialty lightweightaggregates (i.e. clay, pumice, perlite, vermiculite).

Aggregates, from different sources, or produced by different methods,may differ considerably in particle shape, size and texture. Shape ofthe aggregates of the present disclosure may be cubical and reasonablyregular, essentially rounded, or angular and irregular. Surface texturemay range from relatively smooth with small exposed pores to irregularwith small to large exposed pores. Particle shape and surface texture ofboth fine and coarse aggregates influence proportioning of mixtures insuch factors as workability, pumpability, fine-to-coarse aggregateratio, cement binder content, and water requirement.

The structural lightweight concrete composition of the presentdisclosure also comprises a fine aggregate. In a preferred embodiment,the structural lightweight concrete composition of the presentdisclosure comprises a fine aggregate having a specific gravity of1.5-3.25, preferably 1.75-3.0, preferably 2.0-2.8, preferably 2.25-2.6.As used herein, water absorption refers to the penetration of water intoaggregate particles with resulting increase in particle weight. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure comprises a fine aggregate having a waterabsorption of 0.1-1.0%, preferably 0.2-0.8%, preferably 0.4-0.6%, orabout 0.5%. In a preferred embodiment, the structural lightweightconcrete composition of the present disclosure has a weight percentageof the fine aggregate ranging from 15-30% relative to the total weightof the composition, preferably 16-28%, preferably 17-25%, preferably18-24%, preferably 19-23%, preferably 20-22% relative to the totalweight of the structural lightweight concrete composition.

In a preferred embodiment, the fine aggregate is sand, preferably dunesand. As used herein, “sand” refers to a naturally occurring granularmaterial composed of finely divided rock and mineral particles. It isdefined by size in being finer than gravel and coarser than silt. Thecomposition of sand varies, depending on the local rock sources andconditions, but the most common constituent of sand is silica (silicondioxide, or SiO₂), usually in the form of quartz. The second most commontype of sand is calcium carbonate, for example aragonite. In terms ofthe present disclosure, the fine aggregate of the concrete compositionmay be silicon dioxide sand, preferably quarzitic silicon dioxide,preferably quarzitic sand, preferably dune sand.

In terms of particle size, sand particles range in diameter from 0.0625mm to 2 mm. An individual particle in this range is termed a sand grain.By definition sand grains are between gravel (particles ranging from 2mm to 64 mm) and silt (particles ranging from 0.004 mm to 0.0625 mm).ISO 14688 grades sands as fines, medium and coarse with ranges of 0.063mm to 0.2 mm to 0.63 mm to 2.0 mm. Sand is also commonly divided intofive subcategories based on size: very fine sand (0.0625-0.125 mmdiameter), fine sand (0.125-0.250 mm diameter), medium sand (0.250-0.500mm diameter), coarse sand (0.500-1.0 mm diameter) and very coarse sand(1.0-2.0 mm diameter). These categories of based on the Krumbein phiscale, where size in ϕ=−log₂ D; wherein D is the particle size in mm. Onthis scale, for sand the value of ϕ varies from −1 to +4, with thedivisions. In terms of the present disclosure, the fine aggregate of theconcrete composition may be sand, and may be very fine sand, fine sand,medium sand, or even coarse sand, preferably very fine sand, fine sandor medium sand.

In a preferred embodiment, the fine aggregate of the concretecomposition is sand with an average particle size of less than 700 μm,preferably less than 600 μm, preferably less than 500 μm, preferablyless than 400 μm, preferably less than 300 μm, preferably less than 200μm, preferably less than 100 μm, such as for example 500-700 μm,preferably 525-675 μm, preferably 550-650 μm, preferably 575-625 μm. Asused herein, the coefficient of variation or relative standard deviationis expressed as a percentage and defined as the ratio of the particlesize standard deviation (a) to the particle size mean (μ) multiplied by100. In a preferred embodiment, the fine aggregate of the concretecomposition is sand having a coefficient of variation of less than 35%,preferably less than 30%, preferably less than 25%, preferably less than20%, preferably less than 15%, preferably less than 10%. In a preferredembodiment, the fine aggregate of the concrete composition is sandhaving a particle size distribution ranging from 10% of the averageparticle size to 200% of the average particle size, preferably 50-150%,preferably 75-125%, preferably 80-120%, preferably 90-110%.

In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises sand as fine aggregateand the sand comprises 80-95 wt % of silicon dioxide (SiO₂ or silica)relative to the total weight of the sand, preferably 85-94 wt %,preferably 88-93 wt %, preferably 90-92 wt % of SiO₂ relative to thetotal weight of the sand. The most common constituent of sand is silicondioxide (SiO₂ or silica), usually in the form of quartz, which due toits chemical inertness and considerable hardness, is the most commonmineral resistant to weathering. In a preferred embodiment, thestructural lightweight concrete composition of the present disclosurecomprises sand as fine aggregate and the sand further comprises ferricoxide (Fe₂O₃), aluminum oxide (Al₂O₃), magnesium oxide (MgO), andpotassium oxide (K₂O). These compounds are generally present in lessthan 5 wt % relative to the total weight of the sand, preferably lessthan 4 wt %, preferably less than 3 wt %, such as for example 0.1-2.0 wt%, preferably 0.2-1.0 wt %, preferably 0.4-0.9 wt % relative to thetotal weight of the sand. Other impurities may be present in the sandincluding, but not limited to limestone, gypsum, sand stone, feldspar,granite, magnetite, chlorite, glauconite, basalts, iron, obsidian andthe like or mixtures thereof.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise otherfine aggregates. Exemplary suitable fine aggregates that may be used inaddition to, or in lieu of sand or dune sand include, but are notlimited to, mineral particles of natural or synthetic origin, pumice,expanded clays, expanded schists, expanded glasses, expanded aggregatesbased on marble, granite, slate, ceramic, and the like and mixturesthereof.

The structural lightweight concrete composition of the presentdisclosure also comprises a natural coarse aggregate. In a preferredembodiment, the structural lightweight concrete composition of thepresent disclosure comprises a natural coarse aggregate having aspecific gravity of 0.2-2.8, preferably 0.3-2.6, preferably 0.5-2.2,preferably 0.8-2.0, preferably 1.2-1.8, preferably 1.4-1.6. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure comprises a natural coarse aggregate having awater absorption of 1-80%, preferably 1.5-75%, preferably 2-50%,preferably 5-25%. In a preferred embodiment, the structural lightweightconcrete composition of the present disclosure has a weight percentageof the natural coarse aggregate ranging from 20-45% relative to thetotal weight of the composition, preferably 25-40%, preferably 26-36%,preferably 28-34% relative to the total weight of the structurallightweight concrete composition.

In a preferred embodiment, the natural coarse aggregate compriseslimestone. As used herein, limestone refers to a sedimentary rockcomposed largely of the minerals calcite and aragonite, which aredifferent crystal forms or polymorphs of calcium carbonate (CaCO₃). In apreferred embodiment, the limestone comprises at least 50 wt % calciumcarbonate relative to the total weight of the calcium carbonate,preferably at least 55 wt %, preferably at least 60 wt %, preferably atleast 70 wt %, preferably at least 80 wt % relative to the total weightof the calcium carbonate and up to 20 wt % silicon dioxide relative tothe total weight of the calcium carbonate, preferably up to 18 wt %,preferably up to 16 wt %, preferably up to 12 wt %, preferably up to 10wt % silicon dioxide relative to the total weight of the calciumcarbonate. In certain embodiments, the limestone may contain at least afew wt % of other materials including, but not limited to, quartz,feldspar, clay minerals, pyrite, siderite, chert and other minerals,preferably less than 2 wt %, preferably less than 1 wt %, preferablyless than 0.5 wt % relative to the total weight of the calciumcarbonate. In a preferred embodiment, the structural lightweightconcrete composition of the present disclosure has a weight percentageof the natural coarse aggregate in the form of limestone ranging from1-30% relative to the total weight of the composition, preferably10-28%, preferably 12-25%, preferably 16-22% relative to the totalweight of the structural lightweight concrete composition. In apreferred embodiment, the natural coarse aggregate comprises limestonewith an average particle size in the range of 1-20 mm, preferably 5-20mm, preferably 5-15 mm, preferably 10-15 mm, preferably 11-14 mm,preferably 12-13 mm.

In a preferred embodiment, the natural coarse aggregate comprisesperlite. As used herein, perlite refers to an amorphous volcanic glassthat has a relatively high water content, typically formed by thehydration of obsidian. It occurs naturally and has the unusual propertyof greatly expanding when heated sufficiently. The perlite of thepresent disclosure may refer to perlite or expanded perlite. Perlitesoftens when it reaches temperatures of 800-900° C. Water trapped in thestructure of the material vaporizes and escapes, and this causes theexpansion of the material to 7-16 times its original volume. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure has a weight percentage of the natural coarseaggregate in the form of perlite ranging from 1-10% relative to thetotal weight of the composition, preferably 2-8%, preferably 3-7%,preferably 4-6% relative to the total weight of the structurallightweight concrete composition. In a preferred embodiment, the naturalcoarse aggregate comprises perlite with an average particle size of 1-10mm, preferably 1.5-8 mm, preferably 2-6 mm, preferably 2.5-5 mm,preferably 3-4 mm. In a preferred embodiment, the natural coarseaggregate is perlite comprising 65-80 wt % SiO₂, preferably 70-75 wt %SiO₂ relative to the total weight of the perlite, 10-18 wt % Al₂O₃,preferably 12-15 wt % Al₂O₃ relative to the total weight of the perlite,2-5 wt % Na₂O, preferably 3-4 wt % Na₂O relative to the total weight ofthe perlite, and 2-6 wt % K₂O, preferably 3-5 wt % K₂O relative to thetotal weight of the perlite. In certain embodiments, the perlitecomprises various elements including, but not limited to calcium, iron,magnesium, and oxides thereof in less than 2 wt % relative to the totalweight of the perlite, preferably less than 1 wt % relative to the totalweight of the perlite.

In a preferred embodiment, the natural coarse aggregate comprisesscoria. As used herein, “scoria” or “cinder” refers to a highlyvesicular (pitted with many cavities or vesicles), dark colored volcanicrock that may or may not contain crystals (phenocrysts). It is typicallydark in color (generally dark brown, black or purplish red) and basalticor andesitic in composition. Scoria is relatively low in density as aresult of its numerous macroscopic ellipsoidal vesicles. The holes orvesicles form when gasses that were dissolved in the magma come out ofsolution as it erupts, creating bubbles in the molten rock, some ofwhich are frozen in place as the rock cools and solidifies. Scoriadiffers from pumice, another vesicular volcanic rock, in having largervesicles and thicker vesicle walls, and hence a higher density. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure has a weight percentage of the natural coarseaggregate in the form of scoria ranging from 1-30% relative to the totalweight of the composition, preferably 5-25%, preferably 10-20%,preferably 12-18%, preferably 14-16% relative to the total weight of thestructural lightweight concrete composition. In a preferred embodiment,the natural coarse aggregate comprises scoria with an average particlesize of 1-30 mm, preferably 2-25 mm, preferably 3-20 mm, preferably 4-15mm, preferably 4-10 mm.

In certain embodiments, the natural coarse aggregate comprises mixturesof limestone, perlite and scoria, mixtures of perlite and scoria,mixtures of limestone and scoria and mixtures of limestone and perlite.In certain embodiments, the natural coarse aggregate comprises 30-80 wt% limestone relative to the total weight of the natural coarseaggregate, preferably 40-77 wt %, preferably 50-75 wt % limestonerelative to the total weight of the natural coarse aggregate. In certainembodiments, the natural coarse aggregate comprises 10-30 wt % limestonerelative to the total weight of the natural coarse aggregate. In certainembodiments, the natural coarse aggregate comprise 30-90 wt % scoriarelative to the total weight of the natural coarse aggregate, preferably33-50 wt %, preferably 35-45 wt % scoria relative to the total weight ofthe natural coarse aggregate. In certain embodiments, the natural coarseaggregate comprise 10-25 wt % perlite relative to the total weight ofthe natural coarse aggregate, preferably 11-22 wt %, preferably 15-20 wt% perlite relative to the total weight of the natural coarse aggregate.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise othernatural coarse aggregates. Exemplary natural coarse aggregates that maybe used in addition to, or in lieu of limestone, scoria, and/or perliteinclude, but are not limited to, pumice, shale, clays, slate, expandedclays, vermiculite, diatomite, schists, expanded schist and the like andmixtures thereof.

The structural lightweight concrete composition of the presentdisclosure also comprises a synthetic coarse aggregate comprising apolymeric material. As used herein, polymeric material refers to a largesynthetic molecule or macromolecule composed of many repeated subunits.In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises a synthetic coarseaggregate comprising a polymeric material having a specific gravity of0.5-0.99, preferably 0.6-0.95, preferably 0.7-0.92, preferably 0.8-0.9,preferably 0.85-0.89. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure comprises asynthetic coarse aggregate comprising a polymeric material having awater absorption of less than 0.25%, preferably less than 0.10%,preferably less than 0.05%, preferably less than 0.01%. In a preferredembodiment, the structural lightweight concrete composition of thepresent disclosure has a weight percentage of the synthetic coarseaggregate comprising a polymeric material ranging from 2-15% relative tothe total weight of the composition, preferably 3-10%, preferably 4-9%,preferably 5-8% relative to the total weight of the structurallightweight concrete composition.

In a preferred embodiment, the synthetic coarse aggregate comprising apolymeric material is spherical polypropylene beads. In a preferredembodiment, the polypropylene beads are substantially spherical with anaverage particle size of 2-15 mm, preferably 2.5-12 mm, preferably 3-10mm, preferably 4-8 mm. In a preferred embodiment, the synthetic coarseaggregate comprising a polymeric material of the concrete composition ispolypropylene beads having a coefficient of variation of less than 35%,preferably less than 30%, preferably less than 25%, preferably less than20%, preferably less than 15%, preferably less than 10%. In a preferredembodiment, the synthetic coarse aggregate comprising a polymericmaterial of the concrete composition is polypropylene beads having aparticle size distribution ranging from 10% of the average particle sizeto 200% of the average particle size, preferably 50-150%, preferably75-125%, preferably 80-120%, preferably 90-110%. In certain embodiments,the synthetic coarse aggregate comprising a polymeric material mayfurther comprise a variety of polymer additives including, but notlimited to, stabilizers, processing aids, plasticizers, anti-statics,blowing agents, fillers, coupling agents and the like or mixturesthereof.

As used herein polypropylene (PP, polypropene) is a thermoplasticaddition polymer made from the monomer propylene. The relativeorientation of each methyl group relative to the methyl group in theneighboring monomer has a strong effect on the polymer and is termedtacticity. Types of tacticity include isotactic when all methyl groupsare positioned at the same side with respect to the backbone of thepolymer chain, syndiotactic when the positions of the methyl groupsalternate and atactic when the methyl groups of the polypropyleneexhibit no pattern or preferred orientation. In terms of the presentdisclosure the polypropylene may be isotactic, syndiotactic or atactic.Polypropylene may be produced in a manner resulting in a wide molecularweight distribution. In one embodiment, the polypropylene of the presentdisclosure has an average molecular weight of 2-300 kDa, preferably5-200 kDa, preferably 10-150 kDa, preferably 10-75 kDa, preferably 15-50kDa, preferably 20-40 kDa. The degree of polymerization (DP) is definedas the number of monomeric units in a macromolecule or polymer. In oneembodiment, the polypropylene of the present disclosure has a degree ofpolymerization in the range of 100-2500, preferably 150-1500, preferably200-750, preferably 250-500.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise othersynthetic coarse aggregates comprising a polymeric material. Exemplarypolymeric materials or plastic materials that may be used in additionto, or in lieu of polypropylene include, but are not limited to,polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride,polyacrylonitrile, high impact polystyrene, acrylonitrile butadienestyrene, polyethylene/acrylonitrile butadiene styrene,polycarbonate/acrylonitrile butadiene styrene, acrylic polymers,polybutadiene, polyisoprene, polyacetylene, silicones, synthetic rubbersand the like and copolymers and mixtures thereof. In a preferredembodiment, the synthetic coarse aggregate comprising a polymericmaterial is a geosynthetic aggregate made from recycled material andrecyclable polymers and/or plastics including petrochemical byproducts,such as polystyrene, polyethylene, polypropylene and the like.

The structural lightweight concrete composition of the presentdisclosure also comprises an industrial waste byproduct in the form offine particles. As used herein, an “industrial waste byproduct” refersto any waste produced by industrial activity which includes any materialthat is rendered useless during a manufacturing process, such as forexample factories, industries, mills, and mining operations. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure comprises an industrial waste byproduct in theform of fine particles having a specific gravity of 0.4-2.6, preferably0.5-2.2, preferably 0.8-1.8. In a preferred embodiment, the specificgravity of the industrial waste byproduct is less than the specificgravity of the fine aggregate. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure comprises anindustrial waste byproduct in the form of fine particles having a waterabsorption of 0.5-2.0%, preferably 0.75-1.75%, preferably 0.9-1.6%,preferably 1.0-1.5%. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure has a weightpercentage of the industrial waste byproduct in the form of fineparticles ranging from 0.5-10% relative to the total weight of thecomposition, preferably 1-8%, preferably 2-6%, preferably 3-4% relativeto the total weight of the structural lightweight concrete composition.Exemplary industrial waste byproducts may include, but are not limitedto silica fume, a variety of ashes (heavy oil ash, fly ash), a varietyof slags (blast furnace slag, electric arc furnace slag), petrochemicalproduction byproducts, concrete plant byproducts, power plant byproductsand the like.

Mineral admixtures refer to very fine grained inorganic materials thathave pozzolanic or latent hydraulic properties that are added to aconcrete mix to improve the properties of the concrete. The use ofmineral admixtures as partial replacements for cements lowers costs,improves concrete properties and allows for recycling waste. In certainembodiments, the industrial waste byproduct in the form of fineparticles may be considered a mineral admixture. In a preferredembodiment, the industrial waste byproduct is at least one selected fromthe group consisting of silica fume and heavy oil ash.

As used herein, silica fume (or microsilica) refers to an amorphous(non-crystalline) polymorph of silicon dioxide, silica. It is anultrafine powder collected as a by-product in the carbothermic reductionof high purity quartz with carbonaceous materials (i.e. coal, coke,wood) in electric arc furnaces in the production of silicon andferrosilicon alloys. Silica fume is approximately 100 times smaller thanthe average cement particle resulting in a higher surface to volumeratio and a relatively fast pozzolanic reaction. Silica fume isadvantageous in concrete compositions to improve properties including,but not limited to, compressive strength, bond strength, and abrasionresistance. These improvements stem from both the mechanicalimprovements result from the addition of a very fine powder as well asfrom the pozzolanic reactions between the silica fume and free calciumhydroxide in the composition. As used herein, silica fume is not to beused synonymously with fumed silica (pyrogenic silica). The productionprocess, particle characteristics and fields of application of fumedsilica are all different from those of silica fume.

In a preferred embodiment, the industrial waste byproduct is silica fumehaving a BET specific surface area of 5000-50000 m²/kg, preferably10000-40000 m²/kg, preferably 15000-30000 m²/kg. In a preferredembodiment, the industrial waste byproduct is silica fume comprisinggenerally spherical particles with an average particle diameter of lessthan 1000 nm, preferably less than 800 nm, preferably less than 600 nm,preferably less than 400 nm, preferably less than 200 nm, such as forexample 50-300 nm, preferably 75-250 nm, preferably 100-200 nm,preferably 125-175 nm, or about 150 nm. In a preferred embodiment, theindustrial waste byproduct is silica fume as defined using the standardspecifications ASTM C1240 and/or EN 13263 comprising greater than 90% byweight silicon dioxide (SiO₂) relative to the total weight of the silicafume, preferably greater than 91%, preferably greater than 92%,preferably greater than 93%, preferably greater than 94%, preferablygreater than 95% by weight silicon dioxide relative to the total weightof the silica fume. In certain embodiments, the silica fume comprisesvarious elements including, but not limited to, calcium, aluminum, iron,magnesium, potassium, sodium, sulfur and oxides thereof in less than 10wt % relative to the total weight of the silica fume, preferably lessthan 5 wt %, preferably less than 2 wt %, preferably less than 1 wt %relative to the total weight of the silica fume.

As used herein, “heavy oil ash” refers to a residue resulting from thecombustion of heavy oil or cracked oil. Heavy oil is generally definedas fuel oil having relatively long hydrocarbon chains, such as forexample, carbon lengths of between 8-70 carbon atoms, preferably 12-70carbon atoms, preferably 20-70 carbon atoms. As defined by ASTM, heavyfuel oil can be classified as a No. 5 or No. 6 fuel oil. Combustion ofheavy fuel oil produces residue, including ash. Heavy oil ash is a blackpowder type of waste material that results from the burning of heavyoil. Heavy oil ash has unique characteristics compared to other types ofash.

In a preferred embodiment, the industrial waste byproduct is heavy oilash comprising greater than 90% by weight carbon relative to the totalweight of the heavy ash, preferably greater than 91%, preferably greaterthan 92%, preferably greater than 93%, preferably greater than 94%,preferably greater than 95% by weight carbon relative to the totalweight of the heavy ash. In certain embodiments, the heavy oil ashcomprises various elements including, but not limited to, silicon,calcium, aluminum, iron, magnesium, potassium, sodium, vanadium, sulfurand oxides thereof in less than 10 wt % relative to the total weight ofthe heavy oil ash, preferably less than 5 wt %, preferably less than 2wt %, preferably less than 1 wt % relative to the total weight of theheavy oil ash. In a preferred embodiment, the industrial waste byproductis heavy oil ash with an average particle size of less than 20-100 μm,preferably less than 30-80 μm, preferably less than 40-60 μm, preferablyless than 45-50 μm, such as for example less than 100 μm, preferablyless than 90 μm, preferably less than 80 μm, preferably less than 70 μm,preferably less than 60 μm, preferably less than 50 μm.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise otherindustrial waste byproducts in the form of fine particles. Exemplarysuitable industrial waste byproducts that may be used in addition to, orin lieu of silica fume and/or heavy oil ash include, but are not limitedto, limestone fillers, siliceous fillers, fly ash, ground and/orgranulated blast furnace slags, metakaolins and the like and mixturesthereof.

The structural lightweight concrete composition of the presentdisclosure also comprises a superplasticizer. Chemical admixtures referto materials in the form of powder or fluids that are added to theconcrete to give it certain characteristics not obtainable with plainconcrete mixes. In certain embodiments, admixtures may be added to theconcrete at the time of batching and/or mixing. As used herein, a“superplasticizer” or “high range water reducer” refers to a type ofchemical admixture used where a well-dispersed particle suspension isrequired. These polymers are used as dispersants to avoid particlesegregation and to improve the flow characteristics of suspensions suchas in concrete applications. As used herein, a “plasticizer” or“dispersant” is an additive that increases the plasticity or fluidity ofa material. Plasticizers increase the workability of “fresh” concrete,allowing it to be placed more easily, with less consolidating effort. Asuperplasticizer refers to a class of plasticizers that have fewerdeleterious effects and can be used to increase workability more than ispractical with traditional plasticizers. The addition of asuperplasticizer to concrete or mortar allows the reduction of the watercontent and water to cement ratio, while not affecting the workabilityof the mixture. This effect drastically improves the performance of thehardening fresh paste, the strength of concrete increases when the waterto cement ratio decreases. Such treatment improves the strength anddurability characteristics of the concrete and enables the production ofself-consolidating concrete and high performance concrete.

In a preferred embodiment, the superplasticizer is a polycarboxylate,such as for example a polycarboxylate derivative with polyethylene oxideside chains, preferably the superplasticizer is a polycarboxylate ether(PCE) superplasticizer, such as for example the commercially availableGlenium 51. Polycarboxylate ether-based superplasticizers allow asignificant water reduction at a relatively low dosage as a result oftheir chemical structure which enables good particle dispersion.Polycarboxylate ether-based superplasticizers are composed of amethoxy-polyethylene glycol copolymer (side chain) grafted withmethacrylic acid copolymer (main chain). The carboxylate group (COO⁻Na⁺)dissociates in water, providing a negative charge along thepolycarboxylate ether backbone. The polyethylene oxide (PEO or MPEG)group affords a non-uniform distribution of the electron cloud, whichgives a chemical polarity to the side chains. The number and the lengthof side chains are flexible parameters that are easy to change. When theside chains have a large amount of ethylene oxide units, the high molarmass lowers the charge density of the polymer, which decreasesperformance in cement suspensions. To balance both parameters, long sidechain and high charge density, it is often necessary to keep the numberof main chain units much higher than the number of side chain units. Thenegatively charged polycarboxylate ether backbone permits adsorptiononto positively charged cations in a cement water system. The adsorptionof the polymer and its COO⁻ groups changes the zeta potential of thesuspended cement particles yielding electrostatic repulsion forces andsteric hindrance.

It is equally envisaged that the structural lightweight concretecomposition of the present disclosure may be adapted to comprise othersuperplasticizers. Exemplary suitable superplasticizers that may be usedin addition to, or in lieu of a polycarboxylate ether basedsuperplasticizer include, but are not limited to, alkyl citrates,sulfonated naphthalene, sulfonated alene, sulfonated melamine,lignosulfonates, calcium lignosulfonate, naphthalene lignosulfonate,polynaphthalenesulfonates, formaldehyde, sulfonated naphthaleneformaldehyde condensate, acetone formaldehyde condensate,polymelaminesulfonates, sulfonated melamine formaldehyde condensate,polycarbonate, other polycarboxylates, other polycarboxylate derivativescomprising polyethylene oxide side chains, and the like and mixturesthereof.

In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure comprises a superplasticizerhaving a specific gravity of 1.0-2.0, preferably 1.05-1.75, preferably1.10-1.50, preferably 1.20-1.40. In a preferred embodiment, thestructural lightweight concrete composition of the present disclosurehas a weight percentage of the superplasticizer ranging from 0.1-2.0%relative to the total weight of the composition, preferably 0.2-1.6%,preferably 0.3-1.5%, preferably 0.4-1.4%, preferably 0.5-1.2%,preferably 0.6-1.0% relative to the total weight of the structurallightweight concrete composition.

In certain embodiments, the structural lightweight concrete compositionof the present disclosure may further comprise one or more additionalchemical admixtures. Exemplary additional chemical admixtures include,but are not limited to, accelerators, retarders, air entraining agents,pigments, corrosion inhibitors, bonding agents, pumping aids and thelike. Accelerators speed up the hydration (hardening) of concrete andmay be especially useful for modifying the properties of concrete incold weather. Exemplary accelerators include, but are not limited to,CaCl₂, Ca(NO₃)₂ and NaNO₃. Retarders, such as polyol retarders, slow thehydration of concrete and may be used in large or difficult pours wherepartial setting before the pour is complete is undesirable. Exemplaryretarders include, but are not limited to, sugar, sucrose, sodiumgluconate, glucose, citric acid, tartaric acid and the like. Airentraining agents (i.e. surfactants) add and entrain air bubbles in theconcrete, which reduces damage during freeze-thaw cycles, increasingdurability. Entrained air entails a reduction in strength and if toomuch air becomes trapped in the mixing defoamers may be used toencourage the agglomeration of air bubbles causing them to rise to thesurface and disperse. Pigments may be used to change the color of theconcrete, for aesthetics. Corrosion inhibitors may be used to minimizethe corrosion of metal (i.e. steel) that may be used as reinforcement inthe concrete. Bonding agents (typically a polymer) may be used to createa bond between old and new concrete with wide temperature tolerance andcorrosion resistance. Pumping aids improve pumpability, thicken thepaste and reduce separation and bleeding.

In certain embodiments, the structural lightweight concrete compositionof the present disclosure may further comprise a viscosifying agent tomodify the rheological properties of the composition. Exemplaryviscosifying agents include, but are not limited to, cellulose ethers,polysaccharides, hydroxyalkylcelluloses, hydroxyethylcelluloses,methylcellulose, carboxymethylcellulose, hydroxyethylcellulose orethylhydroxyethylcellulose, polyethylene oxides, polyvinyl alcohols,polyamides and the like or mixtures thereof.

In certain embodiments, the structural lightweight concrete compositionof the present disclosure may further comprise one or more additionalreinforcements. Concrete is strong in compression, as the aggregateefficiently carries the compression load. However, it is weak in tensionas the cement holding the aggregate in place can crack, allowing thestructure to fail. Reinforced concretes may add exemplary materialsincluding, but not limited to, steel reinforcing bars, steel fibers,glass fibers, carbon fibers, carbon nanofibers, plastic fibers and thelike or mixtures thereof to aid in carrying tensile loads.

As used herein, unit weight (γ, also known as specific weight) is theweight per unit volume of a material. The unit weight of structurallightweight concrete composition of the present disclosure will varydepending on the composition of the aggregates and the unit weights ofthe constituent aggregates. In a preferred embodiment, the structurallightweight concrete composition of the present disclosure in any of itsembodiments has a unit weight in the range of 1600-1900 kg/m³ aftersetting for up to 30 days, preferably up to 28 days, preferably1650-1850 kg/m³, preferably 1700-1825 kg/m³, preferably 1750-1800 kg/m³after setting for up to 30 days, preferably up to 28 days.

As used herein, compressive strength is the capacity of a material orstructure to withstand loads tending to reduce size, as opposed totensile strength, which withstands loads tending to elongate. In otherwords, compressive strength resists compression (being pushed together),whereas tensile strength resists tension (being pulled apart).Compressive strength can be measured by plotting applied force againstdeformation in a testing machine, such as a universal testing machine.In a preferred embodiment, the structural lightweight concretecomposition of the present disclosure in any of its embodiments has acompressive strength in the range of 20-40 MPa after setting for up to30 days, preferably up to 28 days, preferably up to 14 days, preferablyup to 7 days, preferably 21-35 MPa, preferably 22-30 MPa, preferably23-28 MPa, preferably 24-26 MPa after setting for up to 30 days,preferably up to 28 days, preferably up to 14 days, preferably up to 7days.

As used herein, thermal conductivity is the property of a material toconduct heat or alternatively the ability of a material to absorb heat.It can also be defined as the quantity of heat transmitted through aunit thickness of a material due to a unit temperature or the ratiobetween the heat flux and the temperature gradient. Heat transfer occursat a lower rate across materials of low thermal conductivity than acrossmaterials of high thermal conductivity. Correspondingly, materials ofhigh thermal conductivity are widely used in heat sink applications andmaterials of low thermal conductivity are used as thermal insulation.The SI units for thermal conductivity is measured in watts per meterkelvin (W/(m·K)). The conductivity of concrete depends on itscomposition. In a preferred embodiment, the structural lightweightconcrete composition of the present disclosure in any of its embodimentshas a thermal conductivity in the range of 0.3-0.7 W/(m·K), aftersetting for up to 30 days, preferably up to 28 days, preferably0.35-0.65 W/(m·K), preferably 0.36-0.60 W/(m·K), preferably 0.38-0.55W/(m·K), preferably 0.40-0.50 W/(m·K), preferably 0.41-0.48 W/(m·K)after setting for up to 30 days, preferably up to 28 days. In apreferred embodiment, the structural lightweight concrete composition ofthe present disclosure in any of its embodiments has a thermalconductivity that is up to 80% less than the thermal conductivity of anormal weight concrete composition, preferably up to 70%, preferably upto 60%, preferably up to 55%, preferably up to 50%, preferably up to45%, preferably up to 40% less than the thermal conductivity of a normalweight concrete composition.

According to a second aspect, the present disclosure relates to a methodfor producing a cast concrete product comprising the structurallightweight concrete composition of the present disclosure in any of itsembodiments comprising i) mixing the cement, the fine aggregate, thenatural coarse aggregate, the synthetic coarse aggregate and theindustrial waste byproduct in the form of fine particles to form a solidcement mixture, ii) adding water and a superplasticizer to the cementmixture to affect hydraulic setting while maintaining a slump in therange of 50-100 mm to form a fluid concrete mixture, and iii) castingthe concrete mixture in a mold to produce a cast concrete product aftersetting.

Concrete production is the process of mixing together the variousingredients (water, aggregate, cement, additives, etc.) to produceconcrete. Concrete production is time sensitive. Thorough mixing isessential for the production of uniform high quality concrete. Equipmentand methods should be capable of effectively mixing concrete materialscontaining the largest specified aggregate to produce uniform mixtures.Exemplary equipment includes, but is not limited to concrete drum mixer,a volumetric concrete mixer, or simple concrete mixer. There is a widevariety of equipment for processing concrete from hand tools to heavyindustrial machinery. Whatever the equipment used the objective is toproduce the desired material and ingredients must be properly mixed,placed, shaped and retained within the time constraints.

As used herein, “workability” refers to the ability of a fresh fluidconcrete mix to fill the form/mold properly, optionally with vibration.Workability depends on water content, aggregate (shape and sizedistribution), cementitious content and level of hydration, it can bemodified by the addition of a superplasticizer. Workability can bemeasured by the concrete slump test, a simplistic measure of theplasticity of a fresh batch of concrete following the ASTM C 143 or EN12350-2 test standards. In one embodiment, slump is measured by fillingan “Abram's cone” with a sample from a fresh batch of concrete. The coneis placed with the wide end down onto a level surface; it is then filledin three layers of equal volume, with each layer being tamped with asteel rod to consolidate the layer. When the cone is carefully liftedoff, the enclosed material slumps a certain amount due to gravity. Arelatively dry sample slumps less than a relatively wet sample. In apreferred embodiment, water and superplasticizer are added in dosagesand at a rate to maintain a slump of 50-150 mm, preferably 75-125 mm,preferably about 100 mm. In certain embodiments, one or more aggregatesor a portion of one or more aggregates may be prewetted and/or saturatedwith water. In certain embodiments, a separate paste mixing method maybe used where cement and water are mixed into a paste such as by a highspeed shear type mixer before combining these materials with aggregatesor additives, preferably at a water to cement ratio of less than 0.45,preferably less than 0.4, preferably less than 0.35. In certainembodiments, up to half the batch water may be added to the solidingredients and this premix may be blended with the remaining batchwater and superplasticizer in dosages to maintain optimal slump.

As used herein, casting refers to the process in which a fluid material(i.e. the concrete mixture) is poured into a mold, which contains ahollow cavity of the desired shape, and then allowed to solidify. Thesolidified part is also known as a casting, which is ejected, demoldedor broken out of the mold to complete the process. Concrete is preparedas a viscous fluid so that it may be poured into forms to give theconcrete its desired shape. There are many different ways in whichconcrete formwork can be prepared, such as slip forming and steel plateconstruction or factory setting in the manufacturing of precast concreteproducts. In certain embodiments, the method may further comprise curingprocedures. Cement is hydraulic and water allows it to gain strength,curing allows calcium-silicate hydrate (C—S—H) to form. Hydration andhardening of concrete is critical in the first 3 days, in approximately4 weeks, typically over 90% of the final concrete strength is reached.During this period concrete must be kept under controlled temperatureand humid atmosphere. In a preferred embodiment, this is achieved byspraying or ponding the concrete surfaces with water. In a preferredembodiment, the cast concrete products are demolded after greater than 6hours, preferably greater than 12 hours, preferably greater than 24hours and submerged in a curing chamber (or water tank) maintaining atleast 50% humidity, preferably at least 75% humidity, preferably atleast 90% humidity, preferably at least 100% humidity for greater than 7days, preferably greater than 14 days, preferably greater than 28 days.In certain embodiments, the curing procedure may further compriseincreases in temperature or pressure for intermittent periods of timedepending on the desired properties of the cast concrete product.

According to a third aspect, the present disclosure relates to a castconcrete product comprising the structural lightweight concretecomposition of the present disclosure in any of its embodiments. As aconstruction material, concrete can be cast in almost any shape desired,and once hardened, can become a structural (load bearing) element.Concrete can be used in the construction of structural elements likepanels, beams, pavements, street furniture, or may make cast in situconcrete for building superstructures like navigation locks, large matfoundations, large breakwaters, roads and dams. These may be suppliedwith concrete mixed on site, or may be provided with “ready mixed”concrete made at permanent mixing sites.

In one embodiment, the cast concrete product may be a concrete masonryunit. As used herein, a concrete masonry unit (CMU) also known as cinderblock, hollow block, concrete brick, concrete block, cement block,besser block, or breeze block refers to a large rectangular block usedin building construction. Concrete blocks may be produced with hollowcenters (cores) to reduce weight or improve insulation. The use ofblockwork allows structures to be built in the traditional masonry stylewith layers (or courses) of staggered blocks. Concrete blocks may comein many sizes, for example 350-450 mm by 180-220 mm by 100-200 mm.Concrete block cores are typically tapered so that the top surface ofthe block (as laid) has a greater surface area on which to spread amortar bed. Most concrete masonry units have two cores, but three andfour core units may also be produced. A core also allows for theinsertion of steel reinforcement, tying individual blocks together inthe assembly, aimed towards greatly increased strength. To hold thereinforcement in proper position and to bond the block to thereinforcement, the cores must be filled with grout (i.e. concrete). Avariety of specialized shapes of concrete masonry units exist to allowspecial construction features. U-shaped blocks or knockout blocks mayhave notches to allow the construction of bond beams or lintelassemblies. Blocks with a channel on the end or “jamb blocks” allowdoors to be secured to wall assemblies. Blocks with grooved ends permitthe construction of control joints allowing a filler to be anchoredbetween the block ends. Other features such as “bullnoses” may beincorporated. A wide variety of decorative profiles also exist.

Concrete blocks, when built in tandem with concrete columns and tiebeams and reinforced with rebar, are a very common building material forthe load bearing walls of buildings, in what is termed “concrete blockstructure” (CBS) construction. Houses typically employ a concretefoundation and slab with a concrete block wall on the perimeter. Largebuildings typically use large amounts of concrete block; for even largerbuildings, concrete blocks supplement steel I-beams. Concrete masonrycan be used as a structural element in addition to being used as anarchitectural element. Ungrouted, partially grouted, and fully groutedwalls are all feasible. Reinforcement bars can be used both verticallyand horizontally inside the concrete masonry unit to strengthen the walland result in better structural performance.

The examples below are intended to further illustrate methods andprotocols for preparing and characterizing the structural lightweightconcrete compositions of the present disclosure. Further, they areintended to illustrate assessing the properties of these structurallightweight concrete compositions. They are not intended to limit thescope of the claims.

Example 1

General Methods and Materials

Prepared specimens were tested to assess their mechanical and thermalproperties as well as durability characteristics. The followingmaterials were utilized in the preparation of the structural lightweightconcrete mixtures: i) Portland cement, ii) fine aggregate, iii) coarseaggregate, iv) expanded perlite, v) natural lightweight aggregate(Scoria), vi) polypropylene beads, vii) heavy oil ash, viii) silicafume, and ix) superplasticizer. The properties of the above materialsare described below.

Potable water was used in the preparation of all the mixtures and theircuring. A superplasticizer was used to obtain the required slump (100±25mm) in each mixture. The dosages of the superplasticizer were between0.5 and 1.2% of the weight of the cement. The preferred superplasticizerwas Glenium 51 ®. Glenium 51 is a brown liquid in appearance with aspecific gravity at 20° C. of 1.08±0.02 g/cm³, a pH value at 20° C. of7.0±1.0, an alkali content of ≤5.0%0/and a chloride content of ≤0.1%.ASTM C 150 Type I Portland cement with a specific gravity of 3.15 wasutilized in all the mixtures. Table 1 displays the chemical compositionof the cement used. Dune sand with a specific gravity of 2.56 and waterabsorption of 0.5% was used as the fine aggregate in all the mixtures.Table 2 displays the grading of the dune sand fine aggregate.

TABLE 1 Chemical composition of cement Constituent Weight % SiO₂ 20.52Fe₂O₃ 3.8 Al₂O₃ 5.64 CaO 64.35 MgO 2.11 Na₂O 0.19 K₂O 0.36 SO₃ 2.1 Losson ignition 0.7 Alkalis 0.43 (Na₂O + 0.658 K₂O) C₃S 56.7 C₂S 16.05 C₂A8.52 C₄AF 11.56

TABLE 2 Grading of the dune sand fine aggregate ASTM Sieve # Size (mm) %Passing 4 4.75 100 8 2.36 100 16 1.18 100 30 0.600 76 50 0.300 10 1000.150 4

Crushed limestone with a maximum particle size of 12.5 mm was used ascoarse aggregate in all the mixtures. The specific gravity of thecrushed limestone coarse aggregate was 2.60, the water absorption was1.1-1.4%, the fineness modulus was 3.23 and the unit weight was 1845kg/m³. In addition, the crushed limestone coarse aggregate had a 0.32%of material finer than ASTM standard #200 sieve, a loss on abrasion of23.50% and a 0.45% of clay lumps friable fragments. The mineralogicalcomposition of the crushed limestone coarse aggregate was 80% CaCO₃ and20% SiO₂. Table 3 displays the chemical composition of the crushedlimestone coarse aggregate used.

TABLE 3 Chemical composition of crushed limestone coarse aggregateConstituent Weight % CaO 54.97 SiO₂ 0.01 Al₂O₃ 0.17 Fe₂O₃ 0.05 SiO₂ +Al₂O₃ + 0.23 Fe₂O₃ (≥70) MgO 0.64 Loss on ignition 43.66

The additional coarse aggregates were selected from the natural coarseaggregates expanded perlite and scoria and the synthetic coarseaggregate polypropylene beads. The expanded perlite aggregate was agraded material confirming to ASTM C332 Group I. Table 4 displays thechemical composition of the perlite used. Table 5 displays the gradingof the perlite coarse aggregate. The specific gravity of this perlitematerial was 0.355 and the water absorption was 75%. In addition, theexpanded perlite material had a dry loose weight minimum of 60 kg/m³ anda dry loose weight maximum of 150 kg/m³. The natural lightweightaggregate known as Scoria with a specific gravity of 1.5 and a waterabsorption of 22.2% was acquired from a local quarry and used. Inaddition, the scoria coarse aggregate has a fineness modulus of 5.4 anda unit weight of 866 kg/m³. Polypropylene beads were obtained from apetrochemical plant. The specific gravity of the polypropylene beads is0.886 and the water absorption is 0.008%.

TABLE 4 Chemical composition of expanded perlite coarse aggregateConstituent Weight % Silicon 33.8 Aluminum 7.2 Potassium 3.5 Sodium 3.4Iron 0.6 Calcium 0.6 Magnesium 0.2 Trace 0.2 Oxygen (by difference) 47.5Net Total 97 Bound Water 3.0 Total 100

TABLE 5 Grading of the expanded perlite coarse aggregate ASTM Sieve #Size (mm) % Passing 4 4.75 100 8 2.36  85-100 16 1.18 40-85 30 0.60020-60 50 0.300  5-25 100 0.150  0-10

Heavy oil ash is generated during the burning of heavy oil in a powerplant. The specific gravity of the heavy oil ash is 0.6 and the waterabsorption is 1.5%. Table 6 displays the chemical composition of theheavy oil ash used. Silica fume was acquired from a readymix concreteplant. The silica fume has a specific gravity of 2.2 and a waterabsorption of 1.0%. Table 7 displays the chemical composition of thesilica fume used.

TABLE 6 Chemical composition of heavy oil ash industrial waste byproductConstituent Weight % SiO₂ 1.65 CaO 0.45 Al₂O₃ <10 Fe₂O₃ 0.47 MgO 0.48K₂O 0.03 Na₂O 0.53 V₂O₅ 2.65 Sulfur 9.6 Na₂O + (0.658 0.55 K₂O), % Losson ignition 60.6 Moisture % 5.9

TABLE 7 Chemical composition of silica fume industrial waste byproductConstituent Weight % SiO₂ 92.5 Al₂O₃ 0.72 Fe₂O₃ 0.96 CaO 0.48 MgO 1.78SO₃ — K₂O 0.84 Na₂O 0.5 Loss on ignition 1.55

Example 2

Preparation of Structural Lightweight Concrete Mixtures

A cementitious materials content of 400 kg/m³ and a water/cementitiousmaterial (w/cm) ratio of 0.4 were maintained invariant in all of thestructural lightweight concrete mixtures. Expanded perlite was the majorlightweight aggregate component in all mixtures due to its superiorthermal insulating properties. This was used to decrease the weight ofthe concrete in addition to improving the mechanical and thermalproperties as well as the durability characteristics. Table 8 presentsthe details of the quantities of the mixtures used to prepare structurallightweight concretes with superior thermal insulation.

TABLE 8 Details of quantities of the mixtures Percentage by Weight ofConcrete Coarse Aggregates Fine Fines (Filler) Total LimestoneAggregates Silica Heavy Mix Cement, water, Aggregate, Perlite, Scoria,Polypropylene, Sand, Fume, Oil Ash, # % % % % % % % % % 1 28 16 20 6 0 917 0 6 2 23 17 15 6 15 0 18 6 0 3 25 15 21 6 0 9 18 6 0 4 23 14 22 6 0 325 6 0 5 23 14 25 6 0 3 25 3 0 6 23 17 18 6 15 0 18 3 0 7 24 16 27 7 0 024 0 2 8 24 17 18 6 12 0 22 0 1 9 24 19 0 4 30 0 21 0 1 10 24 16 16 4 150 21 0 3 11 24 16 12 6 18 0 22 2 0

The mixture constituents were mixed in a 0.7 m³ concrete drum mixer for2 to 3 minutes, and then about half of the water content was added whilethe drum was still rotating until all of the particles had become wet.The measured quantity of the superplasticizer was added gradually to theremaining water which was then added to the mixture. The mixing wascontinued until a uniform consistency was achieved. The mixed concretewas poured into the molds of required sizes and shapes, which weresuitable for determining the properties of the developed structurallightweight concrete. The molds were vibrated until a thin mortar filmappeared on the surface of the specimen. The specimens were covered,after casting, with a plastic sheet for 24 hours in a laboratoryenvironment (22±3° C.) to minimize the loss of water in the mixture.After 24 hours, the specimens were demolded and placed in a tank filledwith water for 28 days for further curing.

Example 3

Evaluation of the Properties of Structural Lightweight Concrete Mixtures

The aim of this study was to develop structural lightweight concretewith the use of natural lightweight aggregates, such as expanded perliteand scoria, artificial aggregates, such as polypropylene, and industrialwaste byproducts, such as heavy oil ash and silica fume. The primarymixtures included i) mixtures with expanded perlite aggregate,polypropylene, and heavy oil ash or silica fume (Table 8, mixtures 1, 3,4 and 5), ii) mixtures with expanded perlite, scoria, and heavy oil ashor silica fume (Table 8, mixtures 2, 6, 8, 9, 10, and 11), and iii)mixtures with expanded perlite (without scoria and polypropylene) andheavy oil ash (Table 8, mixture 7).

The 28-day average unit weight of the specimens was measured on 100mm×100 mm×100 mm cube specimens by determining their weight and volume.The mixtures utilizing expanded perlite aggregate, polypropylene, andheavy oil ash or silica fume have a 28-day unit weight in the range of1674 kg/m³ to 1785 kg/m³ and these values satisfy the unit weightrequirements for structural lightweight concrete. The mixtures utilizingexpanded perlite aggregate, scoria, and heavy oil ash or silica fumehave a 28-day unit weight in the range of 1830 kg/m³ to 1891 kg/m³ andthese values satisfy the unit weight requirements for structurallightweight concrete. The mixtures utilizing expanded perlite (withoutscoria and polypropylene) and heavy oil ash have a 28-day unit weight of1771 kg/m³ and this value is within the unit weight requirements forstructural lightweight concrete.

Compressive strength was determined according to ASTM C 39 standardafter 7, 14, and 28 days of curing in water. The rate of loading appliedwas 3.0 kN/s until the failure of the 100 mm×100 mm×100 mm cube specimenand the compressive strength was then determined by dividing the failureload by the area of the cross section. The mixtures utilizing expandedperlite aggregate, polypropylene, and heavy oil ash or silica fume havea compressive strength that varied from 21.3 MPa to 25.8 MPa and thesevalues are more than the strength requirement for structural lightweightconcrete. The mixtures utilizing expanded perlite aggregate, scoria, andheavy oil ash or silica fume have a compressive strength that variedfrom 21 MPa to 35.4 MPa and these values are more than the strengthrequirement for structural lightweight concrete. The mixtures utilizingexpanded perlite (without scoria and polypropylene) and heavy oil ashhave a compressive strength of 19.7 MPa and this value is slightly lowerthan the strength requirement for structural lightweight concrete of 20MPa.

The thermal conductivity was determined according to ASTM C201 standard.Slab specimens measuring 350 mm×350 mm×50 mm in size were utilized toevaluate the thermal conductivity using a Dynatech guarded hot platethermal conductance measuring system, TCFG-R4-6, under steady stateconditions. The slab specimens were dried in an oven at 70° C. to expelany moisture. Thermocouples were connected at five different locationsin the bottom and top of the specimen which was wrapped in a piece ofsoft and thick cloth to achieve stable test conditions. The mixturesutilizing expanded perlite aggregate, polypropylene, and heavy oil ashor silica fume have a thermal conductivity in the range of 0.413 W/(m·K)to 0.657 W/(m·K), which is low compared to the thermal conductivity ofnormal weight concrete that is in the range of 1.185 W/(m·K) to 1.448W/(m·K) which makes these developed structural lightweight concreteshighly desirable for energy conservation. The mixtures utilizingexpanded perlite aggregate, scoria, and heavy oil ash or silica fumehave a thermal conductivity in the range of 0.362 W/(m·K) to 0.483W/(m·K), which is low compared to the thermal conductivity of normalweight concrete that is in the range of 1.185 W/(m·K) to 1.448 W/(m·K)which makes these developed structural lightweight concretes highlydesirable for energy conservation. The mixtures utilizing expandedperlite (without scoria and polypropylene) and heavy oil ash have athermal conductivity of 0.393 W/(m·K) which is low compared to thethermal conductivity of normal weight concrete that is in the range of1.185 W/(m·K) to 1.448 W/(m·K) which makes this developed structurallightweight concrete material can be utilized for thermal insulationpurposes.

The aim of this study was to develop structural lightweight concreteswith superior thermal performance utilizing natural lightweightaggregates, such as expanded perlite and scoria and artificialaggregates, such as polypropylene as well as industrial wastebyproducts, such as heavy oil ash and silica fume. Concrete mixturesprepared with expanded perlite, polypropylene, and heavy oil ash orsilica fume exhibit very low unit weight, moderate compressive strengthand low thermal conductivity. Concrete mixtures prepared with expandedperlite, scoria, and heavy oil ash or silica fume exhibit low unitweight, high compressive strength and low thermal conductivity. Concretemixtures prepared with expanded perlite, and heavy oil ash exhibit lowunit weight, medium compressive strength and low thermal conductivity.All of the developed structural lightweight concretes have exhibited lowunit weight, acceptable compressive strength and low thermalconductivity. Consequently, they can be utilized as structurallightweight concretes with high thermal insulation. The high thermalinsulation may lead to significant savings in the energy required forair conditioning in hot weather conditions and heating in cold weatherconditions.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

The invention claimed is:
 1. A lightweight concrete product castingmethod, comprising: mixing a cement, a fine aggregate, a natural coarseaggregate, spherical polymeric beads and a industrial waste byproduct inthe form of fine particles to form a solid cement mixture having thefollowing composition: the cement; the fine aggregate; the naturalcoarse aggregate which comprises 10-25 wt % expanded perlite based onthe weight of the natural coarse aggregate; the synthetic coarseaggregate which comprises a spherical polymeric material beads; theindustrial waste byproduct which is in the form of fine particles;wherein the average particle size of the fine aggregate and theindustrial waste byproduct is less than or equal to 1 mm and the averageparticle size of the synthetic coarse aggregate spherical polymericbeads and the natural coarse aggregate is greater than 1 mm; wherein theweight ratio of water to cement is in the range of 0.33 to 0.8 and issufficient to affect hydraulic setting of the cement; and wherein thespherical polymeric beads have a specific gravity of 0.8-0.95; addingwater and a superplasticizer to the cement mixture to affect hydraulicsetting while maintaining a slump in the range of 50-100 mm to form afluid concrete mixture; casting the fluid concrete mixture in apredetermined shape by placing the fluid concrete mixture in a mold toproduce a cast concrete product after setting.
 2. The method of claim 1,wherein the spherical polymeric beads are spherical polypropylene beadspith an average particle size of 4-15 mm.
 3. The method of claim 1,wherein the fine aggregate is sand with an average particle size of lessthan 700 μm.
 4. The method claim 1, wherein the natural coarse aggregatecomprises crushed limestone having an average particle size in the rangeof 1-20 mm.
 5. The method of claim 1, wherein the industrial wastebyproduct is at least one selected from the group consisting of silicafume and heavy oil ash.
 6. The method of claim 1, wherein thesuperplasticizer is a polycarboxylate ether.